AC servo motor
STOBER LM Lean motors
Encoderless synchronous motors in efficiency class IE5 with nominal torque from 2.25 to 25.7 Nm (29.8 Nm stall), run position-controlled by SC6 or SI6 drives to about ±1°.
Key specifications
| Rated torque | 2.25–25.7 Nm |
|---|---|
| Standstill torque (max) | 29.8 Nm |
| Feedback | none (encoderless, via SC6/SI6) |
| Accuracy | positioning ±1°, speed deviation <1% |
| Efficiency | IE5, up to 96% |
| Cooling | convection |
Summarised in our own words from STÖBER Antriebstechnik GmbH + Co. KG's published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Specify Motion is not affiliated with STÖBER Antriebstechnik GmbH + Co. KG. STOBER and LM Lean motors are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a STOBER part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These 3 series from our supply network are the closest match on published figures.
Kinco's current-generation AC servo motor line, matched to the JD2 and FD5P PRO drives. Small-inertia 40-80 mm frames run at 3000 rpm on 220 V; large-inertia 130 and 180 mm frames are 1500 rpm machines reaching 47.8 Nm rated and 7.5 kW, with 23-bit multi-turn absolute encoders as standard.
| Published maximum | LM Lean motors | SMK Series AC Servo Motors (SMK40S/60S… |
|---|---|---|
| Rated torque | 25.7 Nm | 47.8 Nm meets or exceeds |
| Peak torque | — | 119.5 Nm |
| Speed | — | 6,000 rpm |
| Power | — | 7,500 W |
Kinco's established AC servo motor range from 40 to 180 mm frames, covering 50 W to 7.5 kW and up to 48 Nm rated torque. Standard feedback is a 2500-line incremental encoder with Hall commutation, with absolute options and a resolver on the 180 mm frame. Pairs with FD2S and CD2S drives.
| Published maximum | LM Lean motors | SMH Series AC Servo Motors (SMH40S-SMH… |
|---|---|---|
| Rated torque | 25.7 Nm | 48 Nm meets or exceeds |
| Power | — | 7,500 W |
Leadshine's AC servo motors for the EL8/EL7/EL6 drives: ELM1 is the economy line and ELM2 the general-purpose line, both with 23-bit absolute encoders, IP65/IP67 sealing and up to 3.5x overload. The catalogue extends ELM2M to 22 kW and previews a 26-bit ELM3.
View ELM1 / ELM2 AC Servo Motors →Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What an AC servo motor is
An AC servo motor is a permanent-magnet synchronous motor designed for closed-loop control of position, speed and torque. A wound stator is driven by a servo drive with sinusoidal three-phase current, while magnets on the rotor follow the rotating field. A high-resolution encoder or resolver on the shaft feeds position back to the drive, which adjusts current many thousands of times a second. The result is precise, dynamic motion with high peak torque, typically about three times the continuous rating for short periods.
When engineers choose an AC servo motor
Choose an AC servo for machine axes needing fast, accurate motion under varying loads, such as packaging, robotics, machine tools and printing. Compared with steppers, servos keep torque at high speed and cannot silently lose position. The trade-offs are cost and set-up: a servo needs a matched drive, feedback and tuning. For simple, low-speed indexing with a steady load, a stepper may be cheaper. For very low speeds and high torque, a gearbox or direct-drive motor may be needed.
How to specify the STOBER LM Lean motors
Send these with your enquiry and an engineer can confirm the right LM Lean motors variant or an equivalent:
- Continuous and peak torque (Nm)
- Rated and maximum speed (rpm)
- Load inertia and inertia ratio
- Supply voltage: 230 V single-phase or 400 V three-phase
- Feedback: incremental or absolute encoder, resolution (bits)
- Holding brake, IP code and shaft options
- Flange size and mounting (mm)
Common mistakes to avoid
- Sizing on peak torque without checking RMS torque over the cycle
- Ignoring load-to-motor inertia ratio, which makes tuning hard
- Forgetting the brake is for holding, not dynamic stopping
- Using a motor and drive pair that the supplier has not matched
STOBER LM Lean motors: frequently asked questions
What is the STOBER LM Lean motors?
Encoderless synchronous motors in efficiency class IE5 with nominal torque from 2.25 to 25.7 Nm (29.8 Nm stall), run position-controlled by SC6 or SI6 drives to about ±1°. Published series figures include rated torque 2.25 Nm, rated torque 25.7 Nm, standstill torque 29.8 Nm. It is made by STÖBER Antriebstechnik GmbH + Co. KG; Specify Motion can help source it or propose an equivalent.
Who makes the STOBER LM Lean motors?
The STOBER LM Lean motors is made by STOBER (STÖBER Antriebstechnik GmbH + Co. KG) and is listed here for engineers comparing options. Specify Motion is not affiliated with STÖBER Antriebstechnik GmbH + Co. KG; brand names are used only to identify the product.
What is the rated torque of the STOBER LM Lean motors?
The published series minimum rated torque is 2.25 Nm. Individual models and sizes in the LM Lean motors range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the STOBER LM Lean motors?
Yes. On published figures, Kinco SMK Series AC Servo Motors (SMK40S/60S/80S, SMK130G, SMK180G) and Kinco SMH Series AC Servo Motors (SMH40S-SMH180D) are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
What is the inertia ratio in servo sizing?
The inertia ratio compares the load inertia reflected to the motor shaft with the motor's rotor inertia. High ratios make the axis harder to tune and slower to settle. Many engineers aim for below about 10:1, and lower for highly dynamic axes, using a gearbox to reduce reflected inertia where needed.
Do AC servo motors need an absolute encoder?
Not always. Incremental encoders need a homing routine after power-up, which is acceptable on many machines. Absolute encoders know their position at power-on, avoiding homing, which saves time and suits robots and multi-axis machines. Multi-turn absolute encoders track turns even when power is off.
Further reading: How to select a servo motor · Servo vs stepper · Servo and stepper motors
Other ac servo motor series
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